Alkali-metal azides are prepared from alkali-metal amide and nitrous oxide. An overall equation illustrative of the process is as follows: EQU 2-NaNH.sub.2 + N.sub.2 O .fwdarw. NaN.sub.3 + NaOH + NH.sub.3 (I)
an azide synthesis process described by U.S. Pat. No. 2,373,800 issued to M. F. Acken et. al. forms sodium azide by the reaction of metallic sodium with excess liquid ammonia followed by reaction of nitrous oxide in the liquid ammonia medium with the so formed sodium amide. The sodium azide product is recovered at the completion of the reaction by adding sufficient methanol to destroy unreacted sodium amide, then evaporating the ammonia reaction medium.
Separation of suspended sodium azide particles from a liquid ammonia slurry has also been accomplished by contacting the slurry with mineral oil, allowing the azide particles to settle with the oil phase or travel through the oil phase for eventual recovery (see U.S. Pat. No. 3,953,582 issued to P. J. Astrawskas). According to another procedure (Japanese Patent Specification W.25353/63 published Nov. 28, 1963), azide removal from a liquid ammonia slurry has been enhanced by adding minor proportions of water to the slurry, but this necessitates subsequent removal of the excess water from the entire volume of liquid ammonia which formed the vehicle for the slurry if the liquid ammonia is to be reused as a solvent/reactant for metallic sodium in a sodium amide formation step.
It is desirable to provide a liquid ammonia based alkali-metal azide preparation and purification process which does not contaminate the azide product or require the inconvenience and expense of dehydrating the predominant part of the liquid ammonia media present during the synthesis cycle.